Animal-human blood transfusion. 17th-century artwork of a blood transfusion from an animal to a human arm (top), and a transfusion between two human arms (bottom). The first documented experiments involving transfusing animal blood into humans took place in the 1660s, including a transfusion from a sheep performed in 1667 by French physician Jean-Baptiste Denys. Transfusing animal blood into humans was soon banned, as it often killed the patients. Artwork from 'Clysmatica nova' (1667) by German naturalist Johann Sigismund Elsholtz (1623-1688).